In a typical liquid crystal display (LCD) device, light emitting diodes (LEDs) are adopted as backlight sources. Specifically, a plurality of LEDs are connected in series to form an LED lightbar; for a large LCD device, a plurality of LED lightbars shall be connected in parallel for use; the LED lightbar is connected in series with a dimming MOS for dimming When the LED lightbars are short-circuited, or two or three LEDs in one LED lightbar are short-circuited, the voltage difference among the LEDs is applied to the dimming MOS in a control integrated circuit (IC), causing heating of the control IC. Thus, generally, when the voltage difference among the LED strings is overhigh, the strings will be switched off for preventing the control IC from heating. However, if the LEDs are switched off, display brightness is inevitably reduced and display quality is affected.